1. Field of the Invention
The present invention relates to a light guiding technique for guiding light emitted from a light source to a light receiving member.
2. Related Art
An endoscope has been widely used to observe the inside of a body cavity in a medical field, etc. The endoscope normally has a light guide for guiding illumination light to an observation site to illuminate the observation site, and a light source device for emitting illumination light and making the illuminated light incident to the light guide is known (for example, see JP-A-2012-105715 and JP-A-2011-200380). Furthermore, LED (Light Emitting Diode) which has a large light amount per unit area in spite of a small light emission point has been practically used.
The light source device generally has a light converging optical system for converging light from the light source to the incident face of the light guide. However, use efficiency of light emitted from LED in the light guide is low in the light converging optical system described above, and thus it has been difficult to efficiently use light of LED as illumination light of an endoscope.